1. Field of the Invention
The present invention relates to a vehicle braking apparatus capable of operating a brake cylinder with a hydraulic braking pressure produced by a master cylinder connected to a vacuum booster and a hydraulic braking pressure produced by a hydraulic pressure pump.
2. Description of the Related Art
A vehicle which travels while automatically maintaining a predetermined intervehicular distance from a preceding vehicle requires an automatic braking apparatus for decelerating the vehicle when the intervehicular distance is short. As such an automatic braking apparatus, it is known that there is an apparatus which causes a master cylinder to produce a predetermined hydraulic braking pressure and operates a brake cylinder by controlling a vacuum booster associated with the master cylinder by means of a linear solenoid.
However, the hydraulic braking pressure which can be produced by the vacuum booster and the master cylinder is not always sufficiently high, and there is a possibility that the required braking force may not be obtained in case of emergency such as panic braking. It is also necessary to provide some kind of backup function to prepare for the occurrence of a failure in the vacuum booster or the master cylinder.